1. Field of the Invention
The present invention relates generally to a copying or duplicating apparatus, and more particularly to a technique for easy and economical recording or reproduction of images or information.
2. Discussion of the Prior Art
As a copying machine, there is known an image-forming apparatus, for example, an electrostatic copier that employs principles of electrostatography. This type of copying machine uses a cylindrical sensitized or photoconductive drum whose outer surface is coated with a photoconductive material such as Se, ZnO, amorphous Si or an organic semiconductor. Areas of the outer surface of the photoconductive drum which correspond to a desired image to be reproduced are exposed to light, and electrostatically charged to form a latent electrostatic image. The latent image is developed by using a toner, and the toner image is then transferred to paper. This type of copying apparatus is characterized by its capability of reproducing images at a comparatively high speed.
3. Problem Solved by the Invention
However, the conventional copying apparatus of the type indicated above employs an optical system for producing the latent images on the photoconductive drum, and therefore requires extremely tight tolerances in the out-of-roundness and dimenional errors of the drum. Accordingly, the cost of manufacture of the drum and consequently the copying apparatus is made considerably high. Further, the electrostatography requires steps of charging the photoconductive medium, developing the latent images, cleaning and erasing the latent images. Repetition of this series of steps will lead to a relatively short life expectancy of the photoconductive medium. Moreover, the apparatus must incorporate complicated devices for performing these steps. The copying machine discussed above suffers from the above drawbacks.